Heat exchangers for automotive vehicles include radiators, oil coolers, or condensers in vehicle air conditioning systems. Many of these heat exchangers utilize tubes carrying oil, coolant or refrigerant and cooling fins, also called air centers, interposed between the tubes to effectively increase the contact with air for heat transfer to the air. A great impetus for increasing the efficiency of heat exchangers has arisen by the need for more fuel efficient and aerodynamic motor vehicles.
The aerodynamic shape of many motor vehicles dictate that the hood line of the motor vehicle be lowered resulting in less space available in the engine compartment particularly in the vertical direction. Two of the largest components in the engine compartment are the radiator and condenser. The lower hood lines dictate for radiators with less core face area. Any decrease in core face area, overall size and weight of the radiator or condenser must therefor be accompanied by an increase in efficiency for heat transfer for a given air flow to provide adequate heat exchange for the oil cooler, radiator and condenser.
Arrangements have been proposed for combining structural and cooling components of radiators and condensers. Some proposals call for the sharing of air centers while other proposals call for the integration of the inlet tanks and outlet tanks of the radiators and condensers by providing sealed chambers within each tank. Other proposals call for incorporating air to oil coolers integrated with the radiator and condenser. Such proposals are described in U.S. Pat. No. 5,009,262 issued to Halstead et al. The integration of the radiator, condenser and oil cooler as taught by U.S. Pat. No. 5,009,262 is incorporated herein by reference.
Heat exchangers for cooling engine oil or transmission fluid, commonly called oil coolers, are often installed in the vehicle radiator so that coolant flows about the exterior of the oil cooler to carry heat away from the oil cooler. This type of oil cooler must be compact in size to fit within a small allocated space inside the engine radiator.
Another type of oil cooler is commonly known as an air-to-oil cooler because it uses air flow about cooling tubes that contain the oil to provide heat transfer from the oil. Both types of oil coolers must be constructed to withstand significant internal oil pressure. They also must have a high heat transfer efficiency to adequately cool the oil passing therethrough.
Due to the properties of oil, namely its high viscosity relative to its low thermal diffusivity, often referred to as a high Prandtl number, thermal boundary layers of the oil need to be broken up throughout the entire oil cooler to increase heat transfer.
What is needed is an improvement arrangement for an oil cooler, with a radiator or condenser for providing sufficient heat exchange in a small integrated package. What is also needed is an oil cooler that is easily constructed and has improved heat transfer efficiency.